Harley engines getting hot in hot weather, isn't anything new. There are alot of UOA'S for Harley engines listed here, that show they really aren't that hard on oil. It seems most owners run synthetic oils in their bikes, and according to the mfgrs and Blackstone labs, they can handle the heat for 5k mile oci's. I've personally owned several Harley's that did not have a factory supplied oil coolers on them, and they lasted upward of 90k miles without engine failure. I know I'm not the only guy that has experienced that. As long as your bike is moving thru air, the oil is going to run at the temps the factory feels is fine for it. It wasn't designed to sit and idle for half an hour. An oil cooler will only add maybe a qt of extra oil to the bikes capacity, but it will also get hot if left to idle for long periods.,,